chapter 13- riboflavin, biotin, and B6

riboflavin- food sources

liver, mushrooms, spinach, and other green leafy vegetables, broccoli, asparagus, milk, and cottage cheese

riboflavin- absorption

in the stomach, HCL releases riboflavin from its bound forms, free riboflavin absorbed via active transport or facilitated diffusion in the small intestine

riboflavin- transport

transported via protein carriers, converted to its coenzyme forms in most tissues, but this occurs mainly in the small intestine, liver, heart, and kidneys

riboflavin- functions

energy metabolism, coenzymes FMN and FAD have oxidation reduction functions, FAD reduced to FADH₂

glossitis

painful, inflamed tongue that can signal a deficiency of riboflavin, niacin, B6, folate, or B12

riboflavin

improve blood pressure control, people with MTHFR have greater risk of hypertension as well as people with Chinese and Mexican heritage

biotin

coenzyme that participates in reaction known as carboxylations that add carbon dioxide to compounds

biotin- food sources

distributed as free vitamin and biocytin which is biotin bound to the amino acid lysine in proteins, whole grains, mushrooms, egg yolks, nuts, legumes

biotin- absorption

in small intestine biotinidase releases biotin from protein and lysine, free biotin is absorbed in the small intestine via a sodium-dependent carrier

biotin- coenzymes

required for the metabolism of carbohydrates, proteins, and fats

biotin- deficiency

rare, infants born with genetic defect that results in low amounts of biotinidase leads to skin rash, hair loss, convulsions, low muscle tone, and impaired growth

B6

nearly all amino acids require B6 coenzyme in their metabolism, B6 has 3 compounds: pyridoxal, pyridoxine, and pyridoxamine

B6- food sources

stored in muscle tissues of animals so meat, fish, and poultry are richest sources, animal sources more readily absorbed

B6- toxicity

only attainable via supplements, cause nerve damage, hand/foot tingling, numbness, TUL is 100mg/day

B6- absorption

passive diffusion, converted to the free vitamin form for absorption, but at high concentrations some of the coenzyme may be absorbed as such

B6- transportation

via the portal vein to the liver, where most of it is phosphorylated, from the liver phosphorylated forms are released for transport in the blood bound the the transport protein albumin, muscle tissue is the main storage site

B6- functions

metabolic reactions, PLP is a coenzyme for reactions which involve nitrogen-containing compound, such as amino groups

B6- deficiency

symptoms include seborrheic dermatitis, microcytic hypochromic anemia (from decreased hemoglobin synthesis), convulsions, depression, confusion

B6- pharmacologic use

treatment for carpal tunnel, PMS, and nausea during pregnancy